There are many environments wherein security systems are employed for the protection of security personnel. Such environments include warehouses or other similar storage facilities where security personnel are employed to prevent theft of merchandise or other stored materials. Another environment where such security systems are employed is in institutions. These include penal institutions or other high security government or private facilities where security personnel are employed to control access to restricted areas by unauthorized persons.
Security systems used in environments of the type mentioned above are required to sense an alarm condition, such as when a security guard is under attack or is otherwise in need of assistance and then locate the relevant alarm area where the alarm condition arose. Accurately locating the relevant alarm area is particularly important because it allows efficient deployment of additional security personnel for responding to the alarm condition.
Although there are many types of security systems, wireless security systems are widely used because of the flexibility in employment and use afforded by such systems. Such systems generally include a central control where security personnel monitor the condition of a plurality of portable alarm transmitters carried by the security personnel throughout the protected facility. Each alarm transmitter is assigned an identification code and includes a transmitter for transmitting the identification code when the alarm transmitter is activated by the wearer. The central control includes a look-up table which relates each identification code to an area of the facility where the wearer, and thus the alarm transmitter, is most likely to be.
When an alarm condition exists, the alarm condition is sensed by one of the alarm transmitters by, for example, the depression of an activation button by the wearer or by a tilt switch and it transmits its identification code by radio frequency signals to the central control. The central control then uses the look-up table to match the received alarm transmitter identification code to the area of the facility where the alarm transmitter is most likely to be and provides the security personnel with that location. The central control can provide the most likely location of the alarm transmitter on either a print-out or on a cathode ray tube map display.
In some systems, the alarm transmitters transmit their respective identification code to the central control indirectly through one or more transponders. In such systems, the alarm transmitters are usually low power transmitters having a limited range which is insufficient for the central control to receive the identification codes. The transponders on the other hand are high power transmitters and receive the alarm transmitter identification codes and relay them to the central control. Each of the transponders can also be assigned an address code and relay both the alarm transmitter identification code and their own address code to the central control when an alarm condition exists.
Prior art systems of the type described above are generally not able to provide an accurate location of an alarmed transmitter. The reason for this is that the alarm transmitters are portable and the security personnel wearing the same are not always able to be in the area corresponding to the identification codes. As a result, when an alarm condition exists, there is always the possibility that the relevant alarm area is not the location where the alarmed transmitter is most likely to be.
It is therefore a general object of the present invention to provide a new and improved security system.
It is a more particular object of the present invention to provide such a system which affords more accurate location of an alarmed transmitter within a protected facility.
It is a more specific object of the present invention to provide such a system which combines transmitted alarm transmitter identification codes and acoustic ranging of the alarmed transmitters to afford more accurate location of the alarmed transmitters.
It is a further object of the present invention to provide a method of sensing an alarm condition in a relevant area and of locating the relevant alarm area.
It is a further object of the present invention to provide an improved alarm transmitter.